In typical drilling operations, especially with deep-drilled holes, the hole is first accurately located by using a spot drill. A spot drill improves the positional accuracy of subsequent drilling operations. After the spot drilling operation is complete, a standard drill is used to drill the hole to the desired depth. A third drill is then typically used to put a chamfer on the edge of the drilled hole. Accordingly, the drilled hole requires at least three drill tools, more if the hole must be trued with a boring cutter and/or reamed to size with a reamer. This takes significant time for at least three operations, requires at least three separate tools, and utilizes at least three tool holder positions on the machine.
One attempt to overcome these problems has involved the development of a combination spot and chamfer drill insert. While this insert was able to reduce the number of operations, the spot point of the insert was constructed with clearance surfaces that were formed at a clearance angle from a projected plane normal to the thickness of the insert. These inserts had excessive clearance at the point which increased the length of the chisel edge resulting in unstable cutting requiring increased thrust and generating more heat at the cut. Therefore, there remains a need in the art for a drill tool insert which can reduce the number of drilling operations to complete a finished drilled hole by combining at least two of operations identified above and having an optimized spot point.